Method for depositing oxide film by thermal ALD and PEALD

ABSTRACT

A method for depositing an oxide film on a substrate by thermal ALD and PEALD, includes: providing a substrate in a reaction chamber; depositing a first oxide film on the substrate by thermal ALD in the reaction chamber; and without breaking a vacuum, continuously depositing a second oxide film on the first oxide film by PEALD in the reaction chamber.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application No. 62/456,953 entitled “METHOD FOR DEPOSITING OXIDE FILM BY THERMAL ALD AND PEALD,” filed Feb. 9, 2017, the disclosure of which is hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention generally relates to a method for depositing an oxide film by thermal atomic layer deposition (thermal ALD) and plasma-enhanced atomic layer deposition (PEALD).

Description of the Related Art

As miniaturization of semiconductor devices progresses, damage to recess patterns or underlying layers caused during semiconductor fabrication processes becomes more problematic. This is because dimensional changes caused by damage to the recess patterns or underlying layers affect the patterning precision more greatly when the devices are miniaturized, resulting in functional degradation. Conventionally, SiO films are used for patterning or used as functional films deposited by PEALD; however, PEALD using direct plasma, i.e., capacitively coupled plasma (CCP), causes damage to recess patterns or underlying layers, and the degree of damage tends to depend on the plasma power, and thus, low RF power has been used for fabricating miniaturized semiconductor devices. Particularly, with carbon-based underlying layers having low resistance to oxidation, application of low RF power is commonly used so as to minimize damage to the underlying layers. When the damage is expressed by a shrinkage of a film, conventionally, the underlying films show typically a shrinkage of about 2 to 5%. However, there is an increasing demand for less film shrinkage in miniaturized devices.

Any discussion of problems and solutions in relation to the related art has been included in this disclosure solely for the purposes of providing a context for the present invention, and should not be taken as an admission that any or all of the discussion was known at the time the invention was made.

SUMMARY OF THE INVENTION

In some embodiments, an oxide film is formed using a continuous two-step process comprising thermal ALD as a first step and PEALD as a second step so as to avoid exposing an underlying layer of the substrate to a plasma, thereby inhibiting dimensional degradation and/or oxidation of the underlying layer. In some embodiments, the first step and the second step are continuously conducted in a same reaction chamber. In some embodiments, since reactivity of the reactant and a precursor for thermal ALD is higher than that for PEALD even when it is in a non-excited state, the reactant is supplied to the reaction chamber in a flow path different for thermal ALD from that for PEALD. The precursor for thermal ALD may or may not be different from that for PEALD.

For purposes of summarizing aspects of the invention and the advantages achieved over the related art, certain objects and advantages of the invention are described in this disclosure. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.

Further aspects, features and advantages of this invention will become apparent from the detailed description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of this invention will now be described with reference to the drawings of preferred embodiments which are intended to illustrate and not to limit the invention. The drawings are greatly simplified for illustrative purposes and are not necessarily to scale.

FIG. 1A is a schematic representation of an ALD (atomic layer deposition) apparatus for thermal ALD and plasma-enhanced ALD (PEALD) depositing an oxide film usable in an embodiment of the present invention.

FIG. 1B illustrates a schematic representation of a precursor supply system using a flow-pass system (FPS) usable in an embodiment of the present invention, wherein (a) represents a state where a carrier gas flows through a bottle to carry a precursor therefrom, and (b) represents a state where the carrier gas bypasses the bottle.

FIG. 2 shows a schematic process sequence of thermal ALD in one cycle according to an embodiment of the present invention wherein a cell in gray represents an ON state whereas a cell in white represents an OFF state, and the width of each column does not represent duration of each process.

FIG. 3 shows a schematic process sequence of thermal ALD in one cycle in combination with a schematic process sequence of PEALD in one cycle according to an embodiment of the present invention wherein a cell in gray represents an ON state whereas a cell in white represents an OFF state, and the width of each column does not represent duration of each process.

FIG. 4 shows a schematic process sequence of PEALD in one cycle according to an embodiment of the present invention wherein a cell in gray represents an ON state whereas a cell in white represents an OFF state, and the width of each column does not represent duration of each process.

FIG. 5 shows a schematic process sequence of thermal ALD in one cycle according to another embodiment of the present invention wherein a cell in gray represents an ON state whereas a cell in white represents an OFF state, and the width of each column does not represent duration of each process.

FIG. 6 shows a schematic process sequence of thermal ALD in one cycle in combination with a schematic process sequence of PEALD in one cycle according to another embodiment of the present invention wherein a cell in gray represents an ON state whereas a cell in white represents an OFF state, and the width of each column does not represent duration of each process.

FIG. 7 is a schematic representation of an ALD (atomic layer deposition) apparatus for thermal ALD and plasma-enhanced ALD (PEALD) depositing an oxide film usable in another embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

In this disclosure, “gas” may include vaporized solid and/or liquid and may be constituted by a single gas or a mixture of gases, depending on the context. Likewise, an article “a” or “an” refers to a species or a genus including multiple species, depending on the context. In this disclosure, a process gas introduced to a reaction chamber through a showerhead or another port may be comprised of, consist essentially of, or consist of a silicon- or metal-containing precursor and an additive gas. The additive gas may include a reactant gas for oxidizing the precursor, and an inert gas (e.g., noble gas) for exciting the precursor, when RF power is applied to the additive gas. The inert gas may be fed to a reaction chamber as a carrier gas and/or a dilution gas. The precursor and the additive gas can be introduced as a mixed gas or separately to a reaction space. The precursor can be introduced with a carrier gas such as a noble gas. A gas other than the process gas, i.e., a gas introduced without passing through the showerhead, may be used for, e.g., sealing the reaction space, which includes a seal gas such as a noble gas. In some embodiments, the term “precursor” refers generally to a compound that participates in the chemical reaction that produces another compound, and particularly to a compound that constitutes a film matrix or a main skeleton of a film, whereas the term “reactant” refers to a compound, other than precursors, that activates a precursor, modifies a precursor, or catalyzes a reaction of a precursor, wherein the reactant may provide an element (such as O) to a film matrix and become a part of the film matrix, when RF power is applied. The term “inert gas” refers to a gas that excites a precursor when RF power is applied, but unlike a reactant, it does not become a part of a film matrix.

In some embodiments, “film” refers to a layer continuously extending in a direction perpendicular to a thickness direction substantially without pinholes to cover an entire target or concerned surface, or simply a layer covering a target or concerned surface. In some embodiments, “layer” refers to a structure having a certain thickness formed on a surface or a synonym of film or a non-film structure. A film or layer may be constituted by a discrete single film or layer having certain characteristics or multiple films or layers, and a boundary between adjacent films or layers may or may not be clear and may be established based on physical, chemical, and/or any other characteristics, formation processes or sequence, and/or functions or purposes of the adjacent films or layers. Further, in this disclosure, any two numbers of a variable can constitute a workable range of the variable as the workable range can be determined based on routine work, and any ranges indicated may include or exclude the endpoints. Additionally, any values of variables indicated (regardless of whether they are indicated with “about” or not) may refer to precise values or approximate values and include equivalents, and may refer to average, median, representative, majority, etc. in some embodiments. Further, in this disclosure, the terms “constituted by” and “having” refer independently to “typically or broadly comprising”, “comprising”, “consisting essentially of”, or “consisting of” in some embodiments. In this disclosure, any defined meanings do not necessarily exclude ordinary and customary meanings in some embodiments.

In the present disclosure where conditions and/or structures are not specified, the skilled artisan in the art can readily provide such conditions and/or structures, in view of the present disclosure, as a matter of routine experimentation.

In all of the disclosed embodiments, any element used in an embodiment can be replaced with any elements equivalent thereto, including those explicitly, necessarily, or inherently disclosed herein, for the intended purposes. Further, the present invention can equally be applied to apparatuses and methods.

The embodiments will be explained with respect to preferred embodiments. However, the present invention is not limited to the preferred embodiments.

In an embodiment, a method for depositing an oxide film on a substrate by thermal ALD and PEALD, comprises: providing a substrate in a reaction chamber; depositing a first oxide film on the substrate by thermal ALD in the reaction chamber; and without breaking a vacuum, continuously depositing a second oxide film on the first oxide film by PEALD in the reaction chamber.

In the above, the word “continuously” refers to at least one of the following: without interruption in space (e.g., without moving the substrate), without interruption in flow (e.g., at least one uninterrupted inflow), without being exposed to the ambient atmosphere, and without any material intervening step (except for an auxiliary step such as purging or other negligible step), depending on the embodiment. In this disclosure, “continuous” flow has a constant flow rate (alternatively, even through the flow is “continuous”, its flow rate may be changed with time).

In some embodiments, since as a reactant, a gas containing H₂O or OH group may be used for the thermal ALD, residual moisture may remain inside the reaction chamber, and thus, in order to reduce partial pressure of moisture inside the reaction chamber, by using a reducing gas such as H₂, the residual moisture can be removed from the reaction chamber between the thermal ALD and the PEALD while maintaining continuity of the thermal ALD and the PEALD.

Because the first oxide film is deposited on the underlying layer of the substrate by the thermal ALD without being exposed to a plasma, damage to the underlying layer can effective be suppressed, e.g., dimensional deterioration of a carbon-containing film (e.g., amorphous carbon prepared by a spin-on or CVD process) as the underlying layer which is used for patterning can effectively be suppressed (e.g., a reduction of shrinkage of the underlying layer) during the thermal ALD conducted at a temperature of about 100° C., for example, or oxidation of a silicon substrate as the underlying layer can effectively be suppressed (e.g., a reduction of thickness of an oxidized portion of the underlying layer) during the thermal ALD conducted at a temperature of about 300° C., for example. After the first oxide film is deposited by the thermal ALD, the second oxide film is continuously deposited by the PEALD on the first oxide film. Since the underlying layer is protected by the first oxide film from a plasma used in the PEALD, the underlying layer is not damaged by the PEALD.

In some embodiments, the oxide film is deposited effectively on a substrate having patterned recesses, e.g., trenches. In this disclosure, a recess between adjacent vertical spacers and any other recess pattern are referred to as a “trench”. That is, the trench is any recess pattern including a pattern formed by vertical spacers and which has, in some embodiments, a width of about 20 nm to about 100 nm (typically about 30 nm to about 50 nm) (wherein when the trench has a length substantially the same as the width, it is referred to as a hole/via, and a diameter thereof is about 20 nm to about 100 nm), a depth of about 30 nm to about 100 nm (typically about 40 nm to about 60 nm), and an aspect ratio of about 1 to about 10 (typically about 2 to about 5). The proper dimensions of the trench may vary depending on the process conditions, film compositions, intended applications, etc.

The film quality of the first oxide film by the thermal ALD is not as good as that of the second oxide film by the PEALD, and thus, by continuously conducting the thermal ALD and the PEALD in the same reaction chamber, exposure of the first oxide film to the ambient atmosphere (e.g., air) is avoided in order to protect the surface of the first oxide film. Typically, the first oxide film has a higher wet etch rate and a lower density than those of the second oxide film. Since the first and second oxide films are continuously deposited, a film constituted by the first and second oxide films is considered to be a single oxide film by ALD, wherein the first oxide film functions as a protective layer, whereas the second oxide film functions as a bulk layer which determines or controls overall properties of the combined oxide film. In some embodiments, the first oxide film has a thickness of about 1 nm to about 7 nm (e.g., about 2 nm to 5 nm), and the second film has a thickness of about 5 nm to about 30 nm (e.g., about 8 nm to 20 nm), wherein the second film is thicker than the first film.

Although the first oxide film by the thermal ALD and the second oxide film by the PEALD are continuously deposited, the boundary or interface therebetween can be manifested or identified by composition analysis by SIMS (Secondary ion mass spectrometry), for example, which shows changes in concentrations of Si, O, H, C, etc. at the boundary or interface. For example, when the first oxide film by the thermal ALD and the second oxide film by the PEALD are both deposited at a same temperature (e.g., 100° C.), since reactivity is weaker in the thermal ALD than in the PEALD, the first oxide film has higher concentrations of carbon and moisture than the second oxide film, even when using the same precursor. Structural observation by STEM (Scanning Transmission Electron Microscopy) may not be able to manifest the boundary or interface.

In some embodiments, a cycle of the thermal ALD comprises feeding a precursor to the reaction chamber, said precursor being a gas of at least one compound selected from the group consisting of aminosilane, silylamine, isocyanatesilane, isothonatesilane, inorganic silane, silane-containing hydroxide, and silane-containing alkoxide. In some embodiments, the precursor contains a metal in place of silicon, such as Ti, Zr, and Hf, forming a film constituted by TiO, ZrO, and HfO, for example.

In some embodiments, a cycle of the thermal ALD comprises feeding a reactant to the reaction chamber, said reactant being at least one gas selected from the group consisting of H₂O, ether, alcohol (e.g., methanol ethanol, etc.), a mixture of H₂ and O₂, and H₂O₂. This reactant can be excited without a plasma so as to react with the precursor adsorbed on the surface of the substrate. Thus, although there are typically three ways to feed the reactant to the reaction chamber (i.e., feeding the reactant to the reaction chamber by introducing the reactant to a manifold conduit upstream of a showerhead provided inside the reaction chamber, by introducing the reactant at the showerhead, and/or by introducing the reactant between the showerhead and a susceptor on which the substrate is placed), depending on the reactivity of the reactant, a proper feeding method should be selected.

In some embodiments, a cycle of the PELAD comprises feeding a precursor in a pulse using a carrier gas which continuously flows to the reaction chamber, and continuously feeding a reactant to the reaction chamber. In some embodiments, the reactant is at least one gas selected from the group consisting of O₂, CO₂, and N₂O.

In some embodiments, a cycle of the thermal ALD comprises feeding a reactant to the reaction chamber, which reactant is at least one gas selected from the group consisting of ethanol, H₂O, and O₃, continuously through the cycle. When the reactivity of the reactant is not high, the reactant can continuously flow through the reaction chamber. However, since the reactivity is low, it takes a long time to complete deposition of a film having a desired thickness. Thus, in some embodiments, a cycle of the thermal ALD comprises feeding a catalytic gas to the reaction chamber in a pulse, which is a gas other than a precursor and a reactant and is capable of promoting deposition of the oxide film in the cycle. By feeding the catalytic gas, the deposition rate of film can significantly be improved for the thermal ALD, and it makes it possible to continuously flow the reactant gas whose reactivity can be low. When the reactant continuously flows not only in the PEALD but also in the thermal ALD, although different reactants may be required for the thermal ALD and the PEALD, the pressure inside the reaction chamber can substantially be constant throughout the cycle of the thermal ALD and the cycle of the PEALD.

In some embodiments, the catalytic gas is a gas of at least one compound selected from the group consisting of pyridine, alkyl metal, pyridylsilane, silylamine, and silazane.

In some embodiments, the deposition method further comprises cleaning the reaction chamber after conducting the deposition by the thermal ALD and the PEALD. The same cleaning process can be conducted after the thermal ALD and the PEALD. In some embodiments, the cleaning is conducted using a cleaning gas by feeding the cleaning gas upstream of a position where a precursor and a reactant are mixed in a gas mixing chamber so that the gas mixing chamber, the passage of the showerhead, the reaction chamber, the passage for exhaust, etc. can be cleaned. In some embodiments, the cleaning gas is excited by a remote plasma unit upstream of the reaction chamber or excited in-situ using a fluorine-containing gas (e.g., ClF₃). In some embodiments, cleaning is conducted after every n number of repeating deposition cycles constituted by a cycle of the thermal ALD and a cycle of the PEALD, wherein the n number of repetitions is fewer than a number of repetitions at which unwanted film deposited on an inner wall of the reaction chamber, etc. starts peeling off from the inner wall, thereby generating contaminant particles.

The embodiments will be explained with respect to the drawings. However, the present invention is not limited to the drawings.

FIG. 2 shows a schematic process sequence of thermal ALD in one cycle according to an embodiment of the present invention wherein a cell in gray represents an ON state whereas a cell in white represents an OFF state, and the width of each column does not represent duration of each process. In the sequence illustrated in FIG. 2, the precursor is supplied in a pulse (“Feed”) using a carrier gas and a dilution gas (collectively referred to as “Inert gas”) which are continuously supplied. This can be accomplished using a flow-pass system (FPS) wherein a carrier gas line is provided with a detour line having a precursor reservoir (bottle), and the main line and the detour line are switched, wherein when only a carrier gas is intended to be fed to a reaction chamber, the detour line is closed, whereas when both the carrier gas and a precursor gas are intended to be fed to the reaction chamber, the main line is closed and the carrier gas flows through the detour line and flows out from the bottle together with the precursor gas. In this way, the carrier gas can continuously flow into the reaction chamber, and can carry the precursor gas in pulses by switching the main line and the detour line. FIG. 1B illustrates a precursor supply system using a flow-pass system (FPS) according to an embodiment of the present invention (black valves indicate that the valves are closed). As shown in (a) in FIG. 1B, when feeding a precursor to a reaction chamber (not shown), first, a carrier gas such as Ar (or He) flows through a gas line with valves b and c, and then enters a bottle (reservoir) 20. The carrier gas flows out from the bottle 20 while carrying a precursor gas in an amount corresponding to a vapor pressure inside the bottle 20, and flows through a gas line with valves f and e, and is then fed to the reaction chamber together with the precursor. In the above, valves a and d are closed. When feeding only the carrier gas (noble gas) to the reaction chamber, as shown in (b) in FIG. 1B, the carrier gas flows through the gas line with the valve a while bypassing the bottle 20. In the above, valves b, c, d, e, and f are closed.

In FIG. 2, the precursor is provided with the aid of a carrier gas (“Inert gas”). Since ALD is a self-limiting adsorption reaction process, the number of deposited precursor molecules is determined by the number of reactive surface sites and is independent of the precursor exposure after saturation, and a supply of the precursor is such that the reactive surface sites are saturated thereby per cycle. A reactant for deposition reaction is supplied to the reaction chamber in a pulse (“React”) where the reactant is thermally activated (e.g., vapor H₂O) so as to react with sites (e.g., —CH₃) exposed on the surface of the precursor adsorbed on the substrate, while the inert gas is continuously fed to the reaction chamber, without feeding the precursor, thereby forming a monolayer.

As mentioned above, each pulse or phase of each deposition cycle is preferably self-limiting. An excess quantity of precursor is supplied in each phase to saturate the susceptible structure surfaces. Surface saturation ensures precursor occupation of all available reactive sites (subject, for example, to physical size or “steric hindrance” restraints) and thus ensures excellent step coverage. In some embodiments the pulse time of one or more precursors can be reduced such that complete saturation is not achieved and less than a monolayer is adsorbed on the substrate surface. After “Feed”, the reaction chamber is purged (“Purge 1”) where no precursor is fed to the reaction chamber, while the inert gas is continuously fed to the reaction chamber, without supplying the reactant, thereby removing non-chemisorbed precursor and excess gas from the surface of the substrate. After “React”, the reaction space is purged (“Purge 2”) where the inert gas is continuously fed to the reaction chamber, without feeding the precursor and reactant to the reaction chamber, thereby removing by-products and excess gas from the surface of the substrate. Due to the continuous flow of the inert gas entering into the reaction chamber as a constant stream into which the precursor is injected intermittently or in pulses, purging can be conducted efficiently to remove excess gas and by-products quickly from the surface of the layer, thereby efficiently continuing multiple thermal ALD cycles until a desired thickness of the layer is obtained.

FIG. 4 shows a schematic process sequence of PEALD in one cycle according to an embodiment of the present invention wherein a cell in gray represents an ON state whereas a cell in white represents an OFF state, and the width of each column does not represent duration of each process. In the sequence illustrated in FIG. 4, the precursor is supplied in a pulse (“Feed”) using a carrier gas and a dilution gas (collectively referred to as “Inert gas”) which are continuously supplied. This can be accomplished using a flow-pass system (FPS) as described above in relation to the process sequence of FIG. 2.

In FIG. 4, the precursor is provided with the aid of a carrier gas (“Inert gas”). Since ALD is a self-limiting adsorption reaction process, the number of deposited precursor molecules is determined by the number of reactive surface sites and is independent of the precursor exposure after saturation, and a supply of the precursor is such that the reactive surface sites are saturated thereby per cycle. A plasma for deposition is generated by applying RF power in a pulse (“RF”) in situ in a reactant gas (“Reactant”) (e.g., O₂) that flows continuously throughout the deposition cycle, while the inert gas and the reactant are continuously fed to the reaction chamber, without feeding the precursor, thereby forming a monolayer.

As mentioned above in relation to the sequence of FIG. 2, an excess quantity of precursor is supplied to saturate the susceptible structure surfaces. In some embodiments the pulse time of one or more precursors can be reduced such that complete saturation is not achieved and less than a monolayer is adsorbed on the substrate surface. After “Feed”, the reaction space is purged (“Purge 1”) where no precursor is fed to the reaction space, while the inert gas and reactant gas are continuously fed to the reaction space, without applying RF power, thereby removing non-chemisorbed precursor and excess gas from the surface of the substrate. After “RF”, the reaction space is purged (“Purge 2”) where the inert gas and reactant gas are continuously fed to the reaction space, without feeding the precursor and without applying RF power to the reaction space, thereby removing by-products and excess gas from the surface of the substrate. Due to the continuous flow of the reactant gas, and also due to the continuous flow of the inert gas entering into the reaction space as a constant stream into which the precursor is injected intermittently or in pulses, purging can be conducted efficiently to remove excess gas and by-products quickly from the surface of the layer, thereby efficiently continuing multiple PEALD cycles until a desired thickness of the layer is obtained.

FIG. 3 shows a schematic process sequence of thermal ALD in one cycle in combination with a schematic process sequence of PEALD in one cycle according to an embodiment of the present invention wherein a cell in gray represents an ON state whereas a cell in white represents an OFF state, and the width of each column does not represent duration of each process. In this continuous combined process sequence of thermal ALD and PEALD in one cycle, the thermal ALD comprises “Feed 1”, “Purge 1”, “React”, and “Purge 2” which substantially correspond to “Feed”, “Purge 1”, “React”, and “Purge 2” illustrated in FIG. 2, respectively. After repeating the above cycle m times (m is an integer of 1 to 3000, preferably 1 to 500), the PEALD is initiated, which comprises “Feed 2”, “Purge 3”, “RF”, and “Purge 4” which substantially correspond to “Feed”, “Purge 1”, “RF”, and “Purge 2” illustrated in FIG. 4, respectively. The above cycle can be repeated n times (n is an integer of 1 to 1000, preferably 1 to 150). A ratio of n/m may be in a range of 0.1 to 3, preferably 0.2 to 1.

In thermal ALD, the reactivity of reactant is typically low, and thus, the deposition rate is typically low as compared with that of PEALD, unless a reactant having high reactivity, such as alkoxide silane, is used. When the reactant having low reactivity is used, by adding a catalyst such as pyridine, the reactivity can significantly be improved, wherein SiO—H bonds, for example, exposed on the surface of monolayer are weakened by the catalyst, thereby increasing the reactivity of the reactant species and the exposed sites of the adsorbed precursor. FIG. 5 shows a schematic process sequence of thermal ALD in one cycle according to another embodiment of the present invention wherein a cell in gray represents an ON state whereas a cell in white represents an OFF state, and the width of each column does not represent duration of each process. In the sequence illustrated in FIG. 5, the precursor is supplied in a pulse (“Feed 1”) using a carrier gas and a dilution gas (collectively referred to as “Inert gas”) which are continuously supplied. This can be accomplished using a flow-pass system (FPS) as described above in relation to the process sequence of FIG. 2.

In FIG. 5, the precursor is provided with the aid of a carrier gas (“Inert gas”). Since ALD is a self-limiting adsorption reaction process, the number of deposited precursor molecules is determined by the number of reactive surface sites and is independent of the precursor exposure after saturation, and a supply of the precursor is such that the reactive surface sites are saturated thereby per cycle. A catalyst for increasing the reactivity of the reactant and the precursor is supplied to the reaction chamber in a pulse (“Feed 2”) that flows continuously throughout the deposition cycle, while the reactant and the inert gas are continuously fed to the reaction chamber, without feeding the precursor, thereby forming a monolayer. Since the reactivity of the reactant is low, the reactant can flow continuously throughout the cycle, and by supplying the catalyst in a pulse, deposition reaction can be activated. The continuous reactant flow is not known for thermal ALD, and pressure fluctuation can be minimized or substantially suppressed, and controllability is increased.

As mentioned above in relation to the sequence of FIG. 2, an excess quantity of precursor is supplied in each phase to saturate the susceptible structure surfaces. In some embodiments the pulse time of one or more precursors can be reduced such that complete saturation is not achieved and less than a monolayer is adsorbed on the substrate surface. After “Feed 1”, the reaction chamber is purged (“Purge 1”) where no precursor is fed to the reaction chamber, while the inert gas and reactant gas are continuously fed to the reaction space, without supplying the catalyst, thereby removing non-chemisorbed precursor and excess gas from the surface of the substrate. After “Feed 2”, the reaction chamber is purged (“Purge 2”) where the inert gas and reactant gas are continuously fed to the reaction space, without feeding the precursor and without supplying the catalyst to the reaction chamber, thereby removing by-products and excess gas from the surface of the substrate. Due to the continuous flow of the reactant gas, and also due to the continuous flow of the inert gas entering into the reaction space as a constant stream into which the precursor and the catalyst are respectively injected intermittently or in pulses, purging can be conducted efficiently to remove excess gas and by-products quickly from the surface of the layer, thereby efficiently continuing multiple thermal ALD cycles until a desired thickness of the layer is obtained.

FIG. 6 shows a schematic process sequence of thermal ALD in one cycle in combination with a schematic process sequence of PEALD in one cycle according to another embodiment of the present invention wherein a cell in gray represents an ON state whereas a cell in white represents an OFF state, and the width of each column does not represent duration of each process. In this continuous combined process sequence of thermal ALD and PEALD in one cycle, the thermal ALD comprises “Feed 1”, “Purge 1”, “Feed 2”, and “Purge 2” which substantially correspond to those illustrated in FIG. 5, respectively. After repeating the above cycle m times (m is an integer of 1 to 3000, preferably 1 to 1000), the PEALD is initiated, which comprises “Feed 3”, “Purge 3”, “RF”, and “Purge 4” which substantially correspond to “Feed”, “Purge 1”, “RF”, and “Purge 2” illustrated in FIG. 4, respectively. The above cycle can be repeated n times (n is an integer of 1 to 1000, preferably 1 to 150). A ratio of n/m may be in a range of 0.1 to 3, preferably 0.2 to 2. In this sequence, pressure fluctuation can be minimized or substantially suppressed, and controllability is increased.

The process cycle can be performed using any suitable apparatus including an apparatus illustrated in FIG. 1A, for example. FIG. 1A is a schematic representation of an ALD (atomic layer deposition) apparatus for thermal ALD and plasma-enhanced ALD (PEALD) depositing an oxide film, desirably in conjunction with controls programmed to conduct the sequences described below, usable in some embodiments of the present invention. In this figure, by providing a pair of electrically conductive (capacitively coupled) flat-plate electrodes 4, 2 in parallel and facing each other in the interior 11 (reaction zone) of a reaction chamber 3, applying HRF power (13.56 MHz or 27 MHz) 25 to one side, and electrically grounding the other side 12, a plasma is excited between the electrodes. A temperature regulator is provided in a lower stage 2 (the lower electrode), and a temperature of a substrate 1 placed thereon is kept constant at a given temperature. The upper electrode 4 serves as a shower plate as well, and precursor gas and reactant gas (and noble gas) are introduced into the reaction chamber 3 through a gas line 21 and a gas line 22, respectively, and through the shower plate 4 for PEALD. Additionally, in the reaction chamber 3, a circular duct 13 with an exhaust line 7 is provided, through which gas in the interior 11 of the reaction chamber 3 is exhausted. Additionally, a transfer chamber 5 disposed below the reaction chamber 3 is provided with a seal gas line 24 to introduce seal gas into the interior 11 of the reaction chamber 3 via the interior 16 (transfer zone) of the transfer chamber 5 wherein a separation plate 14 for separating the reaction zone and the transfer zone is provided (a gate valve through which a wafer is transferred into or from the transfer chamber 5 is omitted from this figure). The transfer chamber is also provided with an exhaust line 6. In some embodiments, the deposition of multi-element film and surface treatment are performed in the same reaction space, so that all the steps can continuously be conducted without exposing the substrate to air or other oxygen-containing atmosphere.

In some embodiments, for a first oxide film by thermal ALD, a precursor and a reactant different from those used for a second oxide film by PEALD are used, although the first oxide film and the second oxide film constitute a single continuous oxide film (of a single film type). In thermal ALD, the precursor and the reactant tend to react with each other when they are in contact, and thus, in some embodiments, the reactant is supplied to the reaction chamber using a port different from that for supplying a reactant for PEALD. In the apparatus illustrated in FIG. 1A, a reactant for thermal ALD can be supplied to the reaction chamber by introducing the reactant to a manifold conduit 23 through a gas line 27 upstream of the showerhead 4 provided inside the reaction chamber 3, and/or by introducing the reactant at the showerhead 4 through a gas port 18 provided in the showerhead 4, and/or by introducing the reactant between the showerhead 4 and the susceptor 2 on which the substrate 1 is place through a gas port 17 provided in a sidewall of the reaction chamber 3 (hermetically penetrating through the circular duct 13). For thermal ALD, when a different precursor is used, the precursor is supplied to the manifold conduit 23 through a gas line 26. In some embodiments, a remote plasma unit can be used for exciting a gas by supplying excited gas to the manifold conduit 23.

In some embodiments, in the apparatus depicted in FIG. 1A, the system of switching flow of an inactive gas and flow of a precursor gas illustrated in FIG. 1B (described earlier) can be used to introduce the precursor gas in pulses without substantially fluctuating pressure of the reaction chamber.

In some embodiments, a dual chamber reactor (two sections or compartments for processing wafers disposed close to each other) can be used, wherein a reactant gas and a noble gas can be supplied through a shared line whereas a precursor gas is supplied through unshared lines.

A skilled artisan will appreciate that the apparatus includes one or more controller(s) (not shown) programmed or otherwise configured to cause the deposition and reactor cleaning processes described elsewhere herein to be conducted. The controller(s) are communicated with the various power sources, heating systems, pumps, robotics, and gas flow controllers or valves of the reactor, as will be appreciated by the skilled artisan.

FIG. 7 is a schematic representation of an ALD apparatus for thermal ALD and plasma-enhanced ALD (PEALD) depositing an oxide film usable in another embodiment of the present invention. In this apparatus, gas lines 31, 32, 33, and 34 correspond to the gas lines 21, 22, 26, and 27 of the apparatus illustrated in FIG. 1A; an RF source 51 corresponds to the RF source 25 in FIG. 1A; a manifold conduit 41 corresponds to the manifold conduit 23 in FIG. 1A; a showerhead 44 corresponds to the showerhead 4 in FIG. 1A; a reaction chamber 52 corresponds to the reaction chamber 3 in FIG. 1A; an exhaust line 45 corresponds to the exhaust line 6 in FIG. 1A; and a susceptor 43 corresponds to the susceptor 2 in FIG. 1A. Any structures indicated in FIG. 1A can be provided in the apparatus illustrated in FIG. 7. A gate valve 42 is a gate valve for a remote plasma unit. In this apparatus, a catalyst can be supplied to the reaction chamber 52. Since the catalyst is reactive with the precursor, in some embodiments, the catalyst is supplied directly to the reaction chamber 52 without mixing it with the precursor upstream of the showerhead 44. For example, by providing another gas passage with other holes 37 in the showerhead 44 as illustrated in FIG. 7, separated from the gas passage with the holes for the precursor as illustrated in FIG. 1A, the catalyst can be supplied to the gas passage with the holes 37 in the showerhead 44 through a gas line 35, so that the catalyst can be fed to the reaction chamber without contacting the precursor until the catalyst enters into the interior of the reaction chamber 52 (although FIG. 7 shows the passage with the holes 37 distributed only near the outer periphery of the showerhead, the holes 37 can be distributed evenly throughout the entire surface of the showerhead). Alternatively or additionally, the catalyst can be fed to the reaction chamber 52 through a gas port 36 provided in a sidewall of the reaction chamber 52.

In some embodiments, the thermal ALD cycles and the PEALD cycles may be conducted continuously as illustrated in FIG. 3 under the conditions shown in Table 1 below.

TABLE 1 (numbers are approximate) Conditions for first oxide film by thermal ALD Substrate temperature 0 to 500° C. (preferably 50 to 300° C. for patterning; 25 to 100° C. for interlayer insulation, for example) Electrode gap (a thickness of a 2 to 15 mm (preferably 5 to 15 mm) substrate is about 0.7 mm) Pressure 133 to 3000 Pa (preferably 200 to 2000 Pa) Flow rate of 1^(st) reactant (in a pulse) 10 to 10000 sccm (preferably 50 to 2000 sccm) Flow rate of carrier gas (continuous) 500 to 4000 sccm (preferably 1000 to 2000 sccm) Flow rate of dilution gas (continuous) 0.1 to 5 slm (preferably 0.1 to 2 slm) Flow rate of 1^(st) precursor Corresponding to the flow rate of carrier gas Duration of “Feed 1” 0.1 to 5 sec. (preferably 0.1 to 2 sec.) Duration of “Purge 1” 0.1 to 5 sec. (preferably 0.2 to 1 sec.) Duration of “React” 1 to 600 sec. (preferably 10 to 240 sec.) Duration of “Purge 2” 1 to 30 sec. (preferably 1 to 15 sec.) Duration of one cycle 2.2 to 640 sec. (preferably 4 to 100 sec.) Growth rate per cycle (nm/min) 0.1 to 1 (preferably 0.2 to 0.5) on top surface Number of cycles (m times) 1 to 3000 (preferably 1 to 1000) Conditions for second oxide film by PEALD Substrate temperature 0 to 500° C. (preferably 50 to 300° C. for patterning; 25 to 100° C. for interlayer insulation, for example) Electrode gap (a thickness of a 2 to 15 mm (preferably 5 to 15 mm) substrate is about 0.7 mm) Pressure 133 to 3000 Pa (preferably 200 to 2000 Pa) Flow rate of 2^(nd) reactant (continuous) 10 to 5000 sccm (preferably 50 to 2000 sccm) Flow rate of carrier gas (continuous) 500 to 5000 sccm (preferably 1000 to 2000 sccm) or same as in thermal ALD Flow rate of dilution gas (continuous) 0.1 to 5 slm (preferably 0.2 to 2 slm) or same as in thermal ALD Flow rate of 2^(nd) precursor Corresponding to the flow rate of carrier gas RF power (13.56 MHz) for a 300-mm 50 to 2000 W (preferably 50 to 200 W) wafer Duration of “Feed 2” 0.1 to 2 sec. (preferably 0.1 to 1 sec.) Duration of “Purge 3” 0.1 to 2 sec. (preferably 0.2 to 1 sec.) Duration of “RF” 0.1 to 5 sec. (preferably 0.2 to 2 sec.) Duration of “Purge 4” 0.1 to 2 sec. (preferably 0.1 to 1 sec.) Duration of one cycle 0.4 to 11 sec. (preferably 0.6 to 6 sec.) Growth rate per cycle (nm/min) 0.4 to 15 (preferably 1 to 10) on top surface Number of cycles (n times) 10 to 1000 (preferably 50 to 350)

The above indicated RF power for a 300-mm wafer can be converted to W/cm² (wattage per unit area of a wafer) which can apply to a wafer having a different diameter such as 200 mm or 450 mm.

Typically, the thickness of the first oxide film is in a range of about 1 nm to about 7 nm, whereas the thickness of the second oxide film is in a range of about 5 nm to about 30 nm, wherein the thickness of the second oxide film is greater than that of the first oxide film (a desired film thickness can be selected as deemed appropriate according to the application and purpose of film, etc.). The combined oxide film may be used for double-patterning by depositing it on a carbon film (e.g., amorphous carbon) or may be used as an interlayer dielectric film by depositing it on a template (e.g., silicon substrate).

In some embodiments, the thermal ALD cycles and the PEALD cycles may be conducted continuously as illustrated in FIG. 6 under the conditions shown in Table 2 below.

TABLE 2 (numbers are approximate) Conditions for first oxide film by thermal ALD Substrate temperature 25 to 500° C. (preferably 50 to 300° C. for patterning; 25 to 100° C. for interlayer insulation, for example) Electrode gap (a thickness of a 2 to 15 mm (preferably 5 to 10 mm) substrate is about 0.7 mm) Pressure 133 to 3000 Pa (preferably 200 to 2000 Pa) Flow rate of 1^(st) reactant (in a pulse) 10 to 10000 sccm (preferably 50 to 2000 sccm) Flow rate of carrier gas (continuous) 500 to 4000 sccm (preferably 1000 to 2000 sccm) Flow rate of dilution gas (continuous) 0.1 to 5 slm (preferably 0.1 to 2 slm) Flow rate of catalyst (in a pulse) 0.5 to 100 sccm (preferably 1 to 50 sccm, e.g., 1-10 sccm) Flow rate of 1^(st) precursor Corresponding to the flow rate of carrier gas Duration of “Feed 1” 0.1 to 5 sec. (preferably 0.1 to 2 sec.) Duration of “Purge 1” 0.1 to 5 sec. (preferably 0.2 to 1 sec.) Duration of “Feed 2” 1 to 600 sec. (preferably 10 to 240 sec.) Duration of “Purge 2” 1 to 30 sec. (preferably 1 to 15 sec.) Duration of one cycle 2.2 to 640 sec. (preferably 4 to 100 sec.) Growth rate per cycle (nm/min) 0.1 to 1 (preferably 0.2 to 0.5) on top surface Number of cycles (m times) 1 to 3000 (preferably 1 to 1000) Conditions for second oxide film by PEALD Same as in Table 1

The first oxide film and the second oxide film may have properties shown in Table 3 below.

TABLE 3 (numbers are approximate) First oxide film Second oxide film 100:1 DHF; 0.5 to 20 0.2 to 3 Top WER (nm/min) (preferably 1 to 10) (preferably 0.2 to 0.5) Film density (g/cm³) 1.7 to 2.4 2.0 to 2.4 (preferably 1.9 to 2.2) (preferably 2.1 to 2.2)

In the above, the WER of the first oxide film is lower than that of the second oxide film, and the film density of the first oxide film is also lower than that of the second oxide film.

The present invention is further explained with reference to working examples below. However, the examples are not intended to limit the present invention. In the examples where conditions and/or structures are not specified, the skilled artisan in the art can readily provide such conditions and/or structures, in view of the present disclosure, as a matter of routine experimentation. Also, the numbers applied in the specific examples can be modified by a range of at least ±50% in some embodiments, and the numbers are approximate.

EXAMPLES Examples 1 to 5

A silicon oxide film was formed on an amorphous carbon film (having a thickness of 100 nm) formed on a silicon substrate (having a diameter of 300 mm and a thickness of 0.7 mm) having wide trenches with an aspect ratio of 1 (an opening width of 100 nm) and narrow trenches with an aspect ratio of 3.5 (an opening width of 30 nm), by a combined process of thermal ALD and PEALD using a sequence illustrated in FIG. 3 or 4, one cycle of which was conducted under the common conditions shown in Table 4 (process cycle) below using the ALD apparatus illustrated in FIG. 1A and a gas supply system (FPS) illustrated in FIG. 1B with the specific conditions and sequence indicated in Table 5. The first reactant was fed to the reaction chamber through the manifold conduit illustrated in FIG. 1A.

TABLE 4 (numbers are approximate) Common Conditions for Process Cycle Carrier gas and dilution gas Ar Flow rate of carrier gas (continuous) 2 slm Pressure 400 Pa Distance between electrodes 12 mm Thermal Deposited film type SiO ALD Total film thickness See Table 5 1^(st) precursor See Table 5 1^(st) reactant Table 5 Flow rate of 1^(st) reactant (in a pulse) 50 sccm 1^(st) reactant temperature control None (Room temperature) “Feed 1” in FIG. 3 0.3 sec “Purge 1” in FIG. 3 0.3 sec “React” in FIG. 3 3 sec (1 sec for feeding, 2 sec for reaction) “Purge 2” in FIG. 3 0.1 sec PEALD Deposited film type SiO Total film thickness 10 nm 2^(nd) precursor BDEAS (bis(diethylamino)silane) 2^(nd) reactant O₂ Flow rate of 2^(nd) reactant 100 sccm (continuous) RF power (13.56 MHz) 100 W “Feed 2” in FIG. 3 0.3 sec “Purge 3” in FIG. 3 0.3 sec “RF” in FIG. 3 0.2 sec “Purge 4” in FIG. 3 0.1 sec

TABLE 5 (numbers are approximate) First oxide Temp. film thickness Process Sequence (° C.) 1^(st) precursor 1^(st) reactant (mm) *1 PEALD FIG. 4 100 — — — 2 Thermal + PEALD FIG. 3 100 BDEAS Ethanol 2 3 Thermal + PEALD FIG. 3 100 TICS (tetra Ethanol 2 isocyanato silane) 4 Thermal + PEALD FIG. 3 100 BDEAS H₂O 2 5 Thermal + PEALD FIG. 3 100 TICS H₂O 2

In Table 5, the Example numbers with “*” indicate comparative example(s). Each obtained film was evaluated. Table 6 shows the results of evaluation.

TABLE 6 (numbers are approximate) Carbon Sidewall Pattern Thermal film shrinkage coverage loading ALD GPC (%) (%) (%) (nm/cycle) *1 3 95 95 — 2 0.6 95 95 0.001 3 0.3 97 96 0.002 4 0.6 95 95 0.001 5 0.3 94 94 0.002

In Table 6, “Carbon film shrinkage” represents a percentage of a ratio of thickness of the carbon film reduced after deposition of the oxide film to thickness of the carbon film before deposition of the oxide film; “Sidewall coverage” represents a percentage of a ratio of thickness of the oxide film at sidewalls of narrow trenches to thickness of the oxide film at a top surface of the substrate; “Pattern loading” represents a percentage of a ratio of thickness of the oxide film at sidewalls of narrow trenches to thickness of the oxide film at sidewalls of wide trenches; “Thermal ALD GPC” represents growth rate per cycle.

As shown in Table 6, when a silicon oxide film was deposited entirely by PEALD, the underlying carbon film was damaged and showed significant film shrinkage (Example 1), whereas when a silicon oxide film was deposited first by thermal ALD as a protective layer, and then continuously deposited by PEALD as a bulk layer, the underlying carbon film was much less damaged and showed significantly lower film shrinkage (Examples 2-5). Further, as the protective layer, the silicon oxide film by thermal ALD using TICS (Examples 3 and 5) appeared to be better than that using BDEAS (Examples 2 and 4). Additionally, the conformality of the silicon oxide film deposited by the PEALD process (Example 1) and that of the silicon oxide film deposited by the combined process of thermal ALD and PEALD (Examples 2-5) were not significantly different (all of them showed more than a conformality of 90%).

Examples 6 to 11

A silicon oxide film was formed on a silicon substrate in a manner substantially similar to that as described in Examples 1 to 5 except that the oxide film was deposited directly on the silicon substrate without the carbon film with the specific conditions and sequence indicated in Table 7.

TABLE 7 (numbers are approximate) First oxide Temp. film thickness Process Sequence (° C.) 1^(st) precursor 1^(st) reactant (mm) *6 PEALD FIG. 4 400 — — — 7 Thermal + PEALD FIG. 3 300 BDEAS Ethanol 2 8 Thermal + PEALD FIG. 3 300 TICS Ethanol 2 9 Thermal + PEALD FIG. 3 300 TICS Ethanol 5 10 Thermal + PEALD FIG. 3 300 OMCTS Ethanol 5 (octamethyl cyclotetrasil oxane) 11 Thermal + PEALD FIG. 3 300 OMCTS H₂O 5

In Table 7, the Example numbers with “*” indicate comparative example(s). Each obtained film was evaluated. Table 8 shows the results of evaluation.

TABLE 8 (numbers are approximate) Thickness of oxidized Sidewall Pattern Thermal Si substrate coverage loading ALD GPC (nm) (%) (%) (nm/cycle) *6 1.5 95 95 — 7 0.2 96 93 0.0009 8 0.2 94 97 0.002 9 0 98 101 0.002 10 0.2 94 94 0.01 11 0.3 93 96 0.02

In Table 8, “Thickness of oxidized Si substrate” represents a thickness of an oxidized silicon substrate based on observation after deposition of the oxide film.

As shown in Table 8, when a silicon oxide film was deposited entirely by PEALD, the underlying silicon layer was damaged and oxidized (Example 6), whereas when a silicon oxide film was deposited first by thermal ALD as a protective layer, and then continuously deposited by PEALD as a bulk layer, the underlying silicon layer was much less damaged and oxidized (Examples 7-11). Further, as the protective layer, the silicon oxide film by thermal ALD using TICS (Example 9) appeared to be better than that using OMCTS (Examples 10 and 11), and also the silicon oxide film having a thickness of 5 nm (Example 9) was better than that of 2 nm (Example 8). The silicon oxide film deposited by thermal ALD using OMCTS (Examples 10 and 11) showed a significantly higher GPC than that of the silicon oxide film deposited by thermal ALD using TICS (Example 9) (since an alkoxide silane has high reactivity). Additionally, the conformality of the silicon oxide film deposited by the PEALD process (Example 6) and that of the silicon oxide film deposited by the combined process of thermal ALD and PEALD (Examples 7-11) were not significantly different (all of them showed more than 90%).

Examples 12 to 17

A silicon oxide film was formed on an amorphous carbon film in a manner substantially similar to that in Examples 1 to 5, except that the 1^(st) reactant was continuously fed, and a catalyst was added using a sequence illustrated in FIG. 2, 4, 5, or 6, one cycle of which was conducted under the common conditions shown in Table 9 (process cycle) below with the specific conditions and sequence indicated in Table 10. The catalyst was fed to the reaction chamber through the showerhead via the different gas passage illustrated in FIG. 7.

TABLE 9 (numbers are approximate) Common Conditions for Process Cycle Carrier gas and dilution gas Ar Flow rate of carrier gas (continuous) 2 slm Pressure 400 Pa Distance between electrodes 12 mm Thermal Deposited film type SiO ALD Total film thickness See Table 10 1^(st) precursor BDEAS 1^(st) reactant See Table 10 Flow rate of 1^(st) reactant (continuous) 50 sccm 1^(st) reactant temperature control Room temperature Catalyst Pyridine Flow rate of catalyst (in a pulse) 3 sccm “Feed 1” in FIG. 6 0.3 sec “Purge 1” in FIG. 6 0.3 sec “Feed 2” in FIG. 6 5 sec “Purge 2” in FIG. 6 0.1 sec PEALD Deposited film type SiO Total film thickness 10 nm 2^(nd) precursor BDEAS 2^(nd) reactant O₂ Flow rate of 2^(nd) reactant (continuous) 100 sccm RF power (13.56 MHz) 100 W “Feed 2” in FIG. 3 0.3 sec “Purge 3” in FIG. 3 0.3 sec “RF” in FIG. 3 0.2 sec “Purge 4” in FIG. 3 0.1 sec

TABLE 10 (numbers are approximate) First oxide film Temp. thickness Process Sequence (° C.) 1^(st) reactant (mm) *12 PEALD FIG. 4 100 — — *13 Thermal ALD FIG. 2 100 H₂O 10 *14 Thermal ALD FIG. 5 100 H₂O 10 15 Thermal + PEALD FIG. 6 100 H₂O 3 16 Thermal + PEALD FIG. 6 100 H₂O 1 17 Thermal + PEALD FIG. 6 100 Ethanol 1

In Table 10, the Example numbers with “*” indicate comparative example(s). Each obtained film was evaluated. Table 11 shows the results of evaluation.

TABLE 11 (numbers are approximate) Carbon Sidewall Pattern Thermal film shrinkage coverage loading ALD GPC (%) (%) (%) (nm/cycle) *12 3 95 95 −(0.15) *13 0.5 94 94 0.001 *14 0.5 93 96 0.03 15 ~0 97 99 0.04 16 0.5 98 95 0.05 17 0.4 91 92 0.04

In Table 11, the terms correspond to those used in Table 6. In “Thermal ALD GPC”, the number in parentheses shows GPC by PEALD.

As shown in Table 11, when a silicon oxide film was deposited entirely by PEALD, the underlying carbon film was damaged and showed significant film shrinkage (Example 12), whereas when a silicon oxide film was deposited first by thermal ALD as a protective layer, and then continuously deposited by PEALD as a bulk layer (Examples 15-17), and when a silicon oxide film was deposited entirely by thermal ALD (Examples 13 and 14), the underlying carbon film was much less damaged and showed significantly lower film shrinkage. Further, surprisingly, even when depositing the second silicon oxide film by PEALD, by depositing the first silicon oxide film by thermal ALD at a thickness of 1 nm to 3 nm as a protective film before depositing the second silicon oxide film (Examples 15-17), adverse effect of a plasma exerted on the underlying film was completely avoided (the carbon film shrinkage in Examples 15-17 was substantially equivalent to or less than that in Examples 13-14 where only thermal ALD was conducted). The above can also be observed in Example 4 (Table 6) as compared with Example 13 (without using the catalyst). Further, when the catalyst was added in a pulse while continuously feeding the reactant in thermal ALD, the GPC was significantly increased (Examples 14 to 17), as compared with the GPC obtained when no catalyst was added and the reactant was fed in a pulse (Example 13). Also, when the thickness of the first silicon oxide film deposited by thermal ALD was 3 nm, substantially no film shrinkage was detected (Example 15), as compared with the first silicon oxide film having a thickness of 1 nm (Example 16). Additionally, the conformality of the silicon oxide film deposited entirely by the PEALD process (Example 12), that of the silicon oxide film deposited entirely by the thermal ALD process (Examples 13 and 14), and that of the silicon oxide film deposited by the combined process of thermal ALD and PEALD (Examples 15-17) were not significantly different (all of them showed more than a conformality of 90%).

Examples 18 to 21

A silicon oxide film was formed on a silicon substrate in a manner substantially similar to that as described in Examples 12 to 17 except that the oxide film was deposited directly on the silicon substrate without the carbon film with the specific conditions and sequence indicated in Table 12.

TABLE 12 (numbers are approximate) First oxide film Temp. thickness Process Sequence (° C.) 1^(st) reactant (mm) *18 PEALD FIG. 4 400 — — 19 Thermal + PEALD FIG. 6 400 H₂O 3 20 Thermal + PEALD FIG. 6 400 H₂O 1 21 Thermal + PEALD FIG. 6 400 Ethanol 1

In Table 12, the Example numbers with “*” indicate comparative example(s). Each obtained film was evaluated. Table 13 shows the results of evaluation.

TABLE 13 (numbers are approximate) Thickness of oxidized Sidewall Pattern Thermal Si substrate coverage loading ALD GPC (nm) (%) (%) (nm/cycle) *18 1.5 96 93 −(0.1) 19 0.6 96 96 0.03 20 ~0 94 97 0.03 21 0.5 91 93 0.02

In Table 13, the terms correspond to those used in Table 8. In “Thermal ALD GPC”, the number in parentheses shows GPC by PEALD.

As shown in Table 13, when a silicon oxide film was deposited entirely by PEALD, the underlying silicon layer was damaged and oxidized (Example 18), whereas when a silicon oxide film was deposited first by thermal ALD as a protective layer, and then continuously deposited by PEALD as a bulk layer, the underlying layer was much less damaged and oxidized (Examples 19-21). Further, when the catalyst was added in a pulse while continuously feeding the reactant in thermal ALD, the GPC was significantly increased (Example 21), as compared with the GPC obtained when no catalyst was added and the reactant was fed in a pulse (Example 7 in Table 8). Also, when the thickness of the first silicon oxide film deposited by thermal ALD was 3 nm, substantially no oxidation of the underlying silicon layer was detected (Example 19), as compared with the first silicon oxide film having a thickness of 1 nm (Example 20). Additionally, the conformality of the silicon oxide film deposited entirely by the PEALD process (Example 18), and that of the silicon oxide film deposited by the combined process of thermal ALD and PEALD (Examples 19-21) were not significantly different (all of them showed more than a conformality of 90%).

In view of the foregoing, it is confirmed that by a combined continuous process of thermal ALD and PEALD according to embodiments explicitly, necessarily, or inherently disclosed herein, a high-quality oxide film can be deposited substantially without damaging an underlying layer caused by a plasma.

It will be understood by those of skill in the art that numerous and various modifications can be made without departing from the spirit of the present invention. Therefore, it should be clearly understood that the forms of the present invention are illustrative only and are not intended to limit the scope of the present invention. 

We claim:
 1. A method for depositing an oxide film on a substrate by thermal ALD and PEALD, comprising: providing a substrate in a reaction chamber; depositing a first oxide film on the substrate by thermal ALD without a plasma in the reaction chamber; and without breaking a vacuum, continuously depositing a second oxide film on the first oxide film by PEALD in the reaction chamber, wherein a cycle of the thermal ALD comprises feeding a precursor, a reactant, and a catalytic gas to the reaction chamber, wherein the catalytic gas is neither a precursor nor a reactant and catalyzes deposition of the first oxide film by increasing reactivity of the reactant and the precursor, and the catalytic gas is fed in a pulse, without overlapping the feeding of the precursor in a pulse, in the cycle to the reaction chamber where the reactant is present.
 2. The method according to claim 1, wherein a cycle of the thermal ALD comprises feeding a precursor to the reaction chamber, said precursor being a gas of at least one compound selected from the group consisting of aminosilane, silylamine, isocyanatesilane, isothonatesilane, inorganic silane, silane-containing hydroxide, and silane-containing alkoxide.
 3. The method according to claim 1, wherein a cycle of the thermal ALD comprises feeding a reactant to the reaction chamber, said reactant being at least one gas selected from the group consisting of H₂O, ether, alcohol, a mixture of H₂ and O₂, and H₂O₂.
 4. The method according to claim 1, wherein a cycle of the thermal ALD comprises feeding a reactant to the reaction chamber by introducing the reactant to a manifold conduit upstream of a showerhead provided inside the reaction chamber, by introducing the reactant at the showerhead, and/or by introducing the reactant between the showerhead and a susceptor on which the substrate is placed.
 5. The method according to claim 1, wherein a cycle of the PEALD comprises feeding a precursor in a pulse using a carrier gas which continuously flows to the reaction chamber, and continuously feeding a reactant to the reaction chamber.
 6. The method according to claim 5, wherein the reactant is at least one gas selected from the group consisting of O₂, CO₂, and N₂O.
 7. The method according to claim 1, further comprising cleaning the reaction chamber after conducting the deposition by the thermal ALD and the PEALD.
 8. The method according to claim 7, wherein the cleaning is conducted using a cleaning gas by feeding the cleaning gas upstream of a position where a precursor and a reactant are mixed.
 9. The method according to claim 8, wherein the cleaning gas is excited by a remote plasma unit upstream of the reaction chamber or excited in-situ using a fluorine-containing gas.
 10. The method according to claim 1, wherein a cycle of the thermal ALD comprises feeding a reactant to the reaction chamber, which reactant is at least one gas selected from the group consisting of ethanol, H₂O, and O₃, continuously through the cycle.
 11. The method according to claim 1, wherein the catalytic gas is a gas of at least one compound selected from the group consisting of pyridine, alkyl metal, pyridylsilane, silylamine, and silazane.
 12. The method according to claim 1, wherein the first oxide film has a thickness of 1 to 7 nm, and the second oxide film has a thickness of 5 to 30 nm, wherein the second oxide film is thicker than the first oxide film.
 13. The method according to claim 1, wherein a surface of the substrate on which the first oxide film is deposited is constituted by amorphous carbon.
 14. The method according to claim 1, wherein a surface of the substrate on which the first oxide film is deposited is constituted by silicon.
 15. The method according to claim 1, wherein the substrate has patterned recesses, and the first and second oxide films are deposited on the recesses. 